The present invention relates to an electronic copying machine for making a hard copy of the images present on a remote surface such as a writing board.
In recent years, there have been developed electronic copying machines capable of making a hard copy of notes, illustrations or the like written on a writing board either directly or on a sheet placed on or tacked to the writing board, which consist of a video camera and a printer assembled as an integral unit. In one such electronic copying machine, an image of a selected part of the remote surface is optically formed on an image sensor, such as a charge coupled device (CCD), of the video camera and converted into video signals. A printing head of the printer is driven by or according to the video signals, to print the image on a copy paper.
Such electronic copying machines are often used on a table or desk. Because tables or desks and writing boards are usually different in height, an electronic copying machine disposed on a table is not always capable of forming an image of the whole surface of the writing board. To make it possible to cover the whole surface of the writing board, it has been proposed that the electronic copying machine be placed on a table in such a way as to incline the optical axis of the image forming optical system upward at a proper angle relative to the surface of the writing board. This, however, leads to the so-called keystone effect in the copied image. That is, the image of the surface of the writing board formed by the electronic copying machine thus placed on the table has disproportionate vertical magnification relative to horizontal magnification. To eliminate this keystone effect, the electronic copying machine should be displaced vertically so as to dispose the optical axis of the image forming optical system perpendicular to the surface of the writing board. This leads to a somewhat troublesome adjustment of an electronic copying machine disposed on a table, with respect to the writing board.
In one known type of copying machine described in Japanese Unexam. Patent Publ. No. 58-162942, an optical viewfinder is used to observe an area of a remote surface to be copied. In another known type of electronic copying machine described in Japanese Unexam. Patent Publ. No. 58-69173, an electronic viewfinder system including a CRT (cathode ray tube) or an LCD (liquid crystal display) is used to display an image of a remote surface, which is scanned by an image sensor to produce image data which is stored in a digital form in a memory, and defines an area to be copied. In these electronic copying machines, it is quite troublesome to define an area to be copied by viewing the optical or electronic viewfinder. Further, the electronic viewfinder makes the electronic copying machine not only expensive but also bulky and heavy.